1. Field of the Invention
The present invention generally relates to portable telephone terminals and, more particularly, to a portable telephone terminal having an answering function for switching between answer messages in accordance with a caller number and the time, and also to a terminal operable by a remote telephone set using caller number authentication.
2. Description of the Related Art Japanese Laid-Open Patent Application No. 10-66145 discloses a mobile communication terminal having an answering function for switching between answer messages depending on a caller number. A call signal incoming at a called terminal from a calling terminal includes a caller number and control information for controlling the called terminal. The called terminal controls an answering mode and switches between answer messages based on the caller number and the control information. Answer messages for individual expected callers are registered in the called terminal and retrieved according to the flowchart of FIG. 7. Each answer message has associated therewith a message identification number.
Referring to FIG. 7, when it is determined in step ST1001 that there is an incoming call, a determination is made in step ST1002 as to whether the automatic answering mode is activated. When the answering mode is activated, a determination is made in step ST1003 as to whether a calling number is identified. If the calling number is identified, a determination is then made in step ST1005 as to whether the calling number is registered in a directory. If the calling number is registered, a determination is made in step ST1006 as to whether the forced answering mode is on. If it is determined that the forced answering mode is turned on, a determination is made in step ST1007 as to whether a predetermined answer message is to be used to automatically respond to the particular caller. If an affirmative answer is yielded in step ST1007, the answer message for that caller is used for response in step ST1008. If a negative answer is yielded in steps ST1003, ST1005, ST1006 and ST1007, a default answer message is used for response to that caller in step ST1004.
If it is determined in step ST1002 that the answering mode is not activated, similar steps (ST1011, ST1012 and ST1009) are executed. When it is determined in step ST1009 that the forced answering mode is not turned on, a normal voice call proceeds in step ST1010.
Japanese Laid-Open Patent Application No. 10-126495 and Japanese laid-Open Patent Application No. 9-182158 disclose a portable telephone set provided with a capability whereby the portable telephone set, if lost, can be remotely operated by another telephone set so that a dialing operation using the lost portable telephone set is prohibited. Japanese Laid-Open Patent Application No. 10-126495 also discloses a portable telephone set configurable, if lost, for a fixed call destination by feeding a remote operation signal to the lost portable telephone set. Operations related to the memory are prohibited so that the leak of personal information and the illegal use of the portable telephone set are prevented. Japanese Laid-Open Patent Application No. 9-182158 discloses a system wherein a lock preventing an illegal use of a lost portable telephone set is registered in a base station using another telephone set so that call origination by an illegal user is prevented.
A rapidly increasing number of portable telephone sets is being used because of the convenience it provides in enabling communication not bounded by time and place constraints. When a user is not able to answer a call, the answering function is utilized. The related-art mobile communication terminal disclosed in Japanese Laid-Open Patent Application No. 10-66145 is provided with an answering function for switching between answer messages depending on the caller number. However, related-art mobile communication terminals are not capable of switching between answer messages for a particular caller in accordance with the time that a call is received.
A user of a portable telephone set may want to answer a call from a particular caller but does not want to answer a call from the others. The answering function that meets such a requirement should be provided with a forced alert function for alerting a user of a call from a registered caller even when the answering mode is activated.
Another problem with the portable telephone system according to the related art is that an input of a password is required when a user calls a lost portable telephone set and remotely sets up a locked dialing option in the lost telephone set. When the user has forgotten the password, the locked dialing option cannot be set up when necessary.